1. Field of the Invention
This invention relates to an infrared camera and an infrared camera system equipped with the infrared camera and a display unit for displaying image signals obtained by the infrared camera.
2. Description of the Prior Art
Infrared cameras are used for, for example, fire detection, invasion monitoring, and installation monitoring. Furthermore, as shown in FIG. 7, an infrared camera C is mounted on a moving object M, such as a vehicle, and is used for detecting an obstacle by obtaining and displaying images representing the front of the moving object M. In addition, an infrared camera C is mounted on the rear or side of a moving object and is used for, for example, detecting a following moving object or a side moving object or obstacle. Moreover, as shown in FIG. 8, a removable head-mounted helmet H equipped with an infrared camera C and display unit D for displaying images obtained by the infrared camera C is mounted on the head of a person, such as a firefighter, and is used for, for example, to detect a heat source, such as a fire, by supplying power to the infrared camera C and display unit D using a battery B.
FIG. 9 is a block diagram of a conventional infrared camera. In this figure, M is a subject; 1 is an infrared optical system; 2 is an imaging device located on the image-formed plane of the infrared optical system 1; 3 is a device-temperature monitor thermally connected to the imaging device 2; 4 is a direct-current bias power supply connected to the imaging device 2; 5 is a device output-level setting circuit connected to the imaging device 2; 6 is a driver circuit connected to the imaging device 2; 7 is an amplifier connected to the imaging device 2; 8 is an offset-level setting circuit connected to the amplifier 7; 9 is a display processing circuit connected to the amplifier 7; 10 is a sensitivity-correcting data memory connected to the display processing circuit 9; 11 is a defect-correcting data memory connected to the display processing circuit 9; 12 is a thermoelectric device thermally connected to the imaging device 2; 13 is a device operating-temperature setting circuit; 14 is a power-supply circuit connected to the device-temperature monitor 3, the device operating-temperature setting circuit 13, and the thermoelectric device 12. The sensitivity-correcting data memory 10 and defect-correcting data memory 11 are ROMs which have recorded and stored correction data at the time of the test and adjustment of a camera. 15 is a shutter located across an optical path between the infrared optical system 1 and the imaging device 2; 16 is a timing-generating circuit connected to the driver circuit 6, the display processing circuit 9, and the shutter 15; 17 is a device package for housing the imaging device 2, the device-temperature monitor 3, and the thermoelectric device 12; 18 is an infrared window for transmitting infrared rays; 19 is an enclosure. The space sealed by the device package 17 and the infrared window 18 is held in a vacuum and a conventional technical example of such an implementation method can be found in Japanese Patent National Publication No. Hei 7-508384.
FIG. 10 shows the structure of the imaging device 2. For the sake of simplicity, it is assumed that the number of pixels for the imaging device 2 is 2xc3x972. In this figure, 20-23 are infrared-detecting devices; 24-27 are diodes; 28-32 are transistors; 33 is a horizontal scanning circuit; 34 is a vertical scanning circuit. The infrared-detecting devices 20-23 are, for example, microbolometers having a hollow structure described in Japanese Patent National Publication No. Hei 7-509057.
FIG. 11 shows the structure of the display processing circuit 9. In this figure, 35 is an A/D converting circuit; 36 is an offset-correcting data memory; 37 is an offset-correcting circuit; 38 is a sensitivity-correcting circuit; 39 is a defect-correcting circuit; 40 is a D/A converting circuit.
Now, the operation will be described. When power is applied, the power-supply circuit 14 supplies the thermoelectric device 12 with power corresponding to the difference between the output of the device-temperature monitor 3 and that of the device operating-temperature setting circuit 13 and stabilizes the temperature of the imaging device 2 at a constant room temperature set by the device operating-temperature setting circuit 13. This temperature is usually between 20 and 40xc2x0 C. Next, clock signals generated by the timing-generating circuit 16 are sent to the imaging device 2 via the driver circuit 6. The horizontal scanning circuit 33 and vertical scanning circuit 34 having received the clock signals supply bias currents depending on the output of the device output-level setting circuit 5 and on the characteristics of the transistor 32 from the direct-current bias power supply 4 to the infrared-detecting devices 20-23, in order, by turning on the transistors 28-31 in order. The presence of the diodes 24-27 causes a bias current to flow to ground via a selected infrared-detecting device and the transistor 32. Signals corresponding to the resistance value of each infrared-detecting device are output as a potential difference arising between the transistor 32 and the ground and are amplified by the amplifier 7 and are then input to the display processing circuit 9.
The shutter 15 is temporarily closed and the output of the infrared-detecting devices 20-23 exposed to uniform infrared rays, that is to say, voltage corresponding to dispersion specific to the resistance values of the infrared-detecting devices 20-23 is converted to digital signals by the A/D converting circuit 35 and stored into the offset-correcting data memory 36. Next, the shutter 15 is opened and infrared rays emitted from subject M are collected by the infrared optical system 1 and are transmitted through the infrared window 18 and then image-formed on the infrared-detecting devices 20-23. This causes minute temperature rises in the infrared-detecting devices 20-23 of about a few millikelvin corresponding to the intensity of infrared rays emitted from subject M and their resistance values change individually. Under this condition, offset correction is performed in the offset-correcting circuit 37 by subtracting offset-correcting data for each infrared-detecting device.
The sensitivity-correcting data memory 10 stores data regarding dispersion of the sensitivity to a target temperature difference of each infrared-detecting device. Sensitivity correction is performed in the sensitivity-correcting circuit 38 by multiplying stored data for each infrared-detecting device. In addition, the defect-correcting data memory 11 stores the addresses of pixels having a sensitivity outside a prescribed range, that is to say, of defective pixels. The correction of a defective pixel is performed by consecutively using the output for the next pixel on the left side of the defective pixel. After the above correction, signals are converted by the D/A converting circuit 40 to analog video signals, which are output.
A conventional infrared camera has the above structure. Therefore, when it is used at an environment temperature, for example at a temperature below xe2x88x9210xc2x0 C. or above +60xc2x0 C., which is widely different from the operating temperature of the imaging device 2, the amount of heat flowing in or out via thermal resistance between the imaging device 2 and the device package 17, or via the thermal resistance of the electric connections of the imaging device 2 and the device-temperature monitor 3 increases. This will increase the amount of heat emitted or absorbed by the thermoelectric device 12 for stabilizing the imaging device 2 at a constant temperature, resulting in the drawback of higher dissipation power. Moreover, if the difference between the operating temperature of the imaging device 2 and the environment temperature is great and the amount of heat flowing in or out exceeds the ability of the thermoelectric device 12 as a heat pump, there is the drawback that the imaging device 2 cannot be stabilized at a prescribed operating temperature. In addition, at an environment temperature widely different from the operating temperature of the imaging device 2, there exists the drawback that a longer time is necessary to heat the imaging device 2 from the temperature before a start to a target operating temperature at the time of warming up after power application, or to cool the imaging device 2.
The present invention was made in order to remove the above drawbacks and provides an infrared camera and an infrared camera system with lower dissipation power, even at a low or high temperature, a wide range of operating temperature, and a shorter warmup by stabilizing the imaging device 2 at a temperature selected among a plurality of device operating-temperature settings and operating the camera.
An infrared camera according to the present invention comprises an infrared optical system; an imaging device located on the image-formed plane of the infrared optical system; a thermoelectric device thermally connected to the imaging device; a device-temperature monitor thermally connected to the imaging device; a device package for housing the imaging device, the thermoelectric device, and the device-temperature monitor; a plurality of device operating-temperature setting means each having a different device operating-temperature setting; device operating-temperature switching means for switching the output of the plurality of device operating-temperature setting means; drive control means for drive-controlling the thermoelectric device based on the output switched by the device operating-temperature switching means and on the output of the device-temperature monitor; drive means for driving the imaging device; and amplifying means for amplifying the output of the imaging device.
Further, an infrared camera according to a preferred aspect of the present invention includes device output-level compensating means for carrying out adjustment so as to make the output level of the imaging device constant.
In an infrared camera according to a preferred aspect of the present invention, the device output-level compensating means comprises a plurality of direct-current bias power supplies each having a different bias voltage setting and direct-current bias power supply switching means for selecting one of the outputs of the plurality of direct-current bias power supplies and supplying the imaging device with the selected output.
Further, in an infrared camera according to a preferred aspect of the present invention, the device output-level compensating means comprises a plurality of device output-level setting means each having a different device output-level setting and device output-level switching means for selecting one of the outputs of the plurality of device output-level setting means and sending the selected output to the imaging device.
An infrared camera according to a preferred aspect of the present invention includes a plurality of offset-level setting means each having a different offset-level setting and offset-level switching means for selecting one of the outputs of the plurality of offset-level setting means and sending the selected output to the amplifying means.
Further, an infrared camera according to a preferred aspect of the present invention includes display processing means for processing the output of the amplifying means and outputting image signals, a plurality of memories storing a plurality of sensitivity-correcting data corresponding to a plurality of operating temperatures set by the plurality of device operating-temperature setting means, and sensitivity-correcting data switching means for selecting one of the plurality of memories and outputting the contents of the selected memory to the display processing means.
An infrared camera according to a preferred aspect of the present invention includes a plurality of memories storing a plurality of defect-correcting data corresponding to a plurality of operating temperatures set by the plurality of device operating-temperature setting means and defect-correcting data switching means for selecting one of the plurality of memories and outputting the contents of the selected memory to the display processing means.
Further, an infrared camera according to a preferred aspect of the present invention includes an external switch for outputting signals to switch both the connection targets of the device operating-temperature switching means and the direct-current bias power supply switching means.
An infrared camera according to a preferred aspect of the present invention includes an external switch for outputting signals to switch both the connection targets of the device operating-temperature switching means and the device output-level switching means.
Further, an infrared camera according to a preferred aspect of the present invention includes an external switch for outputting signals to switch both the connection targets of the device operating-temperature switching means and the offset-level switching means.
An infrared camera according to a preferred aspect of the present invention includes an external switch for outputting signals to switch both the connection targets of the device operating-temperature switching means and the sensitivity-correcting data switching means.
Further, an infrared camera according to a preferred aspect of the present invention includes an external switch for outputting signals to switch both the connection targets of the device operating-temperature switching means and the defect-correcting data switching means.
An infrared camera according to a preferred aspect of the present invention includes device operating-temperature auto-switching means comprising a temperature sensor, switching temperature setting means for setting a switching temperature, and comparing means for comparing a temperature measurement by the temperature sensor and a temperature set by the switching temperature setting means and outputting switching signals to direct-current bias power supply switching means based on the comparison result.
Further, an infrared camera according to a preferred aspect of the present invention includes device operating-temperature auto-switching means comprising a temperature sensor, switching temperature setting means for setting a switching temperature, and comparing means for comparing a temperature measurement by the temperature sensor and a temperature set by the switching temperature setting means and outputting switching signals to device output-level switching means based on the comparison result.
An infrared camera according to a preferred aspect of the present invention includes device operating-temperature auto-switching means comprising a temperature sensor, switching temperature setting means for setting a switching temperature, and comparing means for comparing a temperature measurement by the temperature sensor and a temperature set by the switching temperature setting means and outputting switching signals to offset-level switching means based on the comparison result.
Further, an infrared camera according to a preferred aspect of the present invention includes device operating-temperature auto-switching means comprising a temperature sensor, switching temperature setting means for setting a switching temperature, and comparing means for comparing a temperature measurement by he temperature sensor and a temperature set by the switching temperature setting means and outputting switching signals to sensitivity-correcting data switching means based on the comparison result.
An infrared camera according to a preferred aspect of the present invention includes device operating-temperature auto-switching means comprising a temperature sensor, switching temperature setting means for setting a switching temperature, and comparing means for comparing a temperature measurement by the temperature sensor and a temperature set by the switching temperature setting means and outputting switching signals to defect-correcting data switching means based on the comparison result.
Further, an infrared camera according to a preferred aspect of the present invention includes the temperature sensor inside an enclosure housing the device package, at least.
An infrared camera according to a preferred aspect of the present invention includes the temperature sensor outside an enclosure housing the device package, at least.
Further, an infrared camera system according to a preferred aspect of the present invention includes a moving object on which an infrared camera according to the present invention is mounted and display means for displaying images obtained by the infrared camera.
An infrared camera system according to a preferred aspect of the present invention includes an infrared camera according to the present invention, display means for displaying images obtained by the infrared camera, fixing means for removably fixing the infrared camera and the display means to a person, and a battery for supplying the infrared camera and the display means with power.